Potential climatic influence on maximum stand carrying capacity for 15 Mediterranean coniferous and broadleaf species

Abstract

Climate change projections for the Mediterranean basin predict a continuous increase in extreme drought and heat episodes, which will affect forest dynamics, structure and composition. Understanding how climate influences the maximum size-density relationship (MSDR) is therefore critical to designing adaptive silvicultural guidelines based on the potential stand carrying capacity of tree species. With this aim, data from the Third Spanish National Forest Inventory (3NFI) and WorldClim databases were used to analyze climate-related variations of the maximum stand carrying capacity for 15 species from the Pinus, Fagus and Quercus genera. First, basic MSDR were fitted using linear quantile regression and observed size-density data from monospecific 3NFI plots. Reference values for maximum stocking, expressed in terms of the Maximum Stand Density Index (SDI max), were estimated by species. Then, climate-dependent MSDR models including 35 annual and seasonal climatic variables were fitted. The best climate-dependent models, based on the Akaike Information Criteria (AIC) index, were used to determine the climatic drivers affecting MSDR, to analyze general and species-specific patterns and to quantify the impact of climate on maximum stand carrying capacity. The results showed that all the selected climate-dependent models improved the goodness of fit over the basic models. Among the climatic variables, spring and summer maximum temperatures were found to be key drivers affecting MSDR for the species studied. A common trend was also found across species, linking warmer and drier conditions to smaller SDI max values. Based on projected climate scenarios, this suggests potential reductions in maximum stocking for these species. In this study, a new index was proposed, the Q index, for evaluating the impact of climate on maximum stand carrying capacity. Our findings highlight the importance of using specific climatic variables to better characterize how they affect MSDR. The models presented in this study will allow us to better explain interactions between climate and MSDR while also providing more precise estimates concerning maximum stocking for different Mediterranean coniferous and broadleaf tree species.

Effects of Thinning on Carbon Storage in a Mixed Broadleaved Plantation in a Subtropical Area of China

“…There is an advantageous growth at low density, as commonly observed in selective or future crop tree thinning systems for individual tree size growth acceleration [46]. Competition reduction enables an increase in stand density, mass production, and climate change mitigation through higher carbon storage [47][48][49]. Thinning reduced the tree layer C (Figure 1A) by removing the trees but promoting the tree biomass C growth by relieving the competition among trees for resources (Table 6).…”

Effects of species mixing on maximum size–density relationships in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.)-dominated mixed forests converted from even-aged pure stands

“…Temperature and rainfall play a significant role in modifying both the slope and intercept of the maximum size–density relationship in a given species ( Kweon and Comeau, 2017 ; Andrews et al., 2018 ; de Prado et al., 2020 ). Latitudinal differences are closely related to climate conditions, which have implications for the growth and distribution of tree species.…”

Species Mixing Proportion and Aridity Influence in the Height–Diameter Relationship for Different Species Mixtures in Mediterranean Forests

“…Competition equivalence coefficient (CEC) compares species-specific growing space requirements of a species with their value in mixed stands, and it is calculated as the ratio of potential carrying capacity of both species in pure stands (by means of maximum stand density index [60]-SDI max ). Since recent studies have shown evidence that SDI max varies with climate [61,62], in this study we obtained climate-dependent CECs (Supplementary Table S2) to calculate species mixing proportions for each species in mixed stands using climate-dependent Maximum Size-Density Relationship (MSDR) models presented by Rodriguez-de-Prado et al [63].…”